1. Field of the Invention
This invention relates to agricultural implements, and more particularly to a tine assembly for a rake in which the tine is torsionally spring-mounted.
2. Description of the Prior Art
In agricultural implements in general, and hay rakes in particular, the rake tines are mounted in a spring-biased mounting assembly so that the tines are urged outwardly while being deflected inwardly during use. The spring bias mounting is necessary for the rake to operate properly. It is important that the spring rate of tine mounting be such that the force necessary to deflect the tine is increased as the tine is deflected, at least through the initial portion of tine deflection, so that the crop is properly moved.
In conventional tine assemblies, the tines are formed as part of a torsional metal spring. The spring is made of heavy wire, approximately 1/4 inch in diameter, formed into a series of coils. Generally, two coils are formed, one clockwise and the other counterclockwise, with the coils connected to each other in the middle, so that they may be mounted to the machine. The wire at the two outer ends of the coils extends tangentially out from the coils to form two tines. In use, the coils supply a torsional spring biasing to the tines, so that if the tines are deflected angularly, the coils provide a counterforce that urges the tines back to their original positions. This conventional tine assembly relies upon the spring rate of a torsional spring to provide a resistance to the tine deflection. Thus, the force necessary to deflect the tine increases as the tine is deflected, and a substantial force must be imparted to the tine to deflect the tine a large amount.
Another tine assembly design avoids the use of a metal spring and, instead, uses a rubber mass to achieve spring biasing. In this design, the tine is formed of a length of heavy wire of desired length, with a ball or head formed at the upper end. The upper end of the tine is then mounted in a rubber mass having the general shape of an inverted teardrop. The wire tine protrudes from the pointed end of this teardrop shape, and a steel mounting plate is attached to the rounded end of this shape. The rubber mass is attached to the top of the tine and to the metal plate by mold bonding. The steel mounting plate is then attached to the machine. The upper end of the tine is spaced from the metal mounting plate to allow angular deflection of the tine relative to the mounting plate. A spring bias is imparted to the tine by the bending properties of the rubber mass, which also produces tension and compression stresses on the rubber-metal intefaces. Therefore, excellent adhesion of the interfaces becomes very important.
While the use of a rubber-metal tine assembly provides advantages over the all-metal tine assembly, there are several disadvantages in the rubber-metal design of the prior art. The design relies upon excellent adhesion between the rubber and metal at the interface, where tension and compression stresses occur. This excellent adhesion is particularly important if the rake encounters an extraordinary feed condition, such as a clogged machine, in which the tines will be subjected to extreme deflection, in which case, very large stresses will be imparted to the rubber-metal interfaces.
If the bonding between the upper end of the tine and the rubber mass fails, or if the bonding between the rubber mass of the mounting plate fails, the tine may drop from the rake into the field or into the equipment.